rize the structure. It should be noted that the region to the left of Aally includes a rotating magnetic disk, a slider that has read and write heads, a suspension arm above the rotating disk and an actuator arm that swings the suspension arm to place the read and/or write heads over selected circular tracks on the rotating disk. The suspension arm biases the slider into contact with the surface of the disk when the disk is not rotating, but, when the disk rotates, air is swirled by the rotating disk adjacent an air bearing surface (ABS) of the slider causing the slider to ride on an air bearing a slight distance from the surface of the rotating disk. When the slider rides on the air bearing the write and read heads are employed for writing magnetic impressions to and reading magnetic signal fields from the rotating disk. The read and write heads are connected to processing circuitry that operates according to a computer program to implement the writing and reading functions.
The volume of information processing in the information age is increasing rapidly. In particular, it is desired that HDDs be able to store more information in their limited area and volume. A technical approach to this desire is to increase the capacity by increasing the recording density of the HDD. To achieve higher recording density, further miniaturization of recording bits is effective, which in turn typically requires the design of smaller and smaller components.
The further miniaturization of the various components, however, presents its own set of challenges and obstacles. In order to produce a higher recording density in a magnetic head installed in a hard disk device, the track pitch may be narrowed and bits for writing to the magnetic medium may be made smaller. As a result, there is a considerable reduction in the area of the main pole at the air bearing surface (ABS). As the main pole in a conventional magnetic head becomes narrower, the recording field decreases, and it is no longer possible to produce the recording field required for writing.
In order to deal with this problem, a method of recording known as high-frequency magnetic field assisted recording or Microwave Assisted Magnetic Recording (MAMR) in which a microwave oscillator, such as a Spin Torque Oscillator (STO) is formed above the magnetic pole, a high-frequency-magnetic field is applied to the magnetic medium in order to reduce the coercive force of the medium, and recording is performed in this state by applying a recording field to the medium. Methods for forming, the STO on a flat main pole have been proposed. However, when the main pole is flat, the head field generated by the main pole is reduced in comparison with a main pole having a conventional shape which is tapered at the trailing side. This means that in order to subsequently increase the recording density, it may be necessary to form the microwave oscillator on the taper which is provided on the trailing side of the main pole in order to alleviate the reduction in the head field.
However, implementing a high assist effect from the microwave magnetic field in order to use MAMR is not sufficient to achieve a high recording density. If the magnetic characteristics of the medium are not appropriately controlled to correspond to the magnetic field of the head, satisfactory recording characteristics will not be obtained even if a high assist effect is obtained.